core

#### Calculate Error Map

(This item pertains to the Measure Probe dialog box. On the Probe Utilities dialog box, accessible through Insert | Hardware Definition | Probe, click on the Measure button.)

Normally, wrist devices are calibrated at relatively small increments (such as 20 degrees). When you calibrate an infinitely indexable wrist, and the Calibrate the Unit check box is selected on the Measure Probe dialog box, PC-DMIS automatically creates a wrist error compensation file named abcomp.dat that it uses to correct for angular errors in the wrist. Creating an error map increases the accuracy of the wrist when used to measure at positions not previously calibrated by allowing PC-DMIS to interpolate the probing offsets.

After calculating the error map, the results are stored on your computer’s hard drive so that any time you use the wrist, it takes advantage of the improved angular accuracy. You should only calculate the error map periodically (once a week or less), or as necessary. When calculating the error map, PC-DMIS also performs a valid wrist and tip calibration for the currently loaded probe file.

You should do a wrist calibration each time the mounting of the wrist changes. Also, refer to your hardware and vendor information for all appropriate times to map a wrist since this can change based on device construction and manufacturer recommendations.

Once the infinitely indexable wrist device is calibrated and a wrist error map file exists, you need to tell PC-DMIS to use the error map file. To do this, from the Probe Utilities dialog box, select the Use Wrist Map If Available check box (For information on this check box, see the "Use Wrist Map If Available check box" topic in the "Defining Hardware" chapter). You can then create and use any position of new probe files with a minimum of calibrations.

To do this, create a new probe file and perform a normal tip calibration using at least one probe position on the qualification tool that maintains a link to probe file used during the Calibrate the Unit process. However, you need to use more then one probe position for this calibration to provide a better "fitting" of the probe offset data to the wrist error matrix. This is especially true if you indent to utilize several wrist positions in the new probe file.

Failure to maintain a link to the probe file used during wrist mapping results in measurement errors.